Turbofan engines typically have a fan with a hub and a plurality of fan blades disposed for rotating about a central axis of the engine. The casing surrounding the fan blades must be able to contain a broken fan blade or blade fragments propelled outwardly from the rotating hub at high speeds during a fan blade-off (FBO) event. Conventionally, a hard wall fan case uses a metallic fan case structure to absorb the energy of the fan blade projectiles during an FBO event. The metallic fan case structure has thick walls to provide adequate strength as required. Some types of soft wall fan cases have also been developed, which allow a fan blade to partially penetrate a thin-walled fan case during an FBO event with energy absorption due to the case penetration. In such soft wall fan cases, energy is typically absorbed by a containment fabric layer, such as fabric containing para-aramid synthetic fiber known as Kevlar®, which has been wrapped around the outside of the fan case. These fan cases may be made of aluminium or other metallic or composite materials. However, it is a challenge to fabricate a soft wall fan case having thinner duct walls while meeting the required structural stiffness and strength.
Accordingly there is a need to provide an improved soft wall fan case.